app.rs

   1use std::{
   2    any::{TypeId, type_name},
   3    cell::{BorrowMutError, Cell, Ref, RefCell, RefMut},
   4    marker::PhantomData,
   5    mem,
   6    ops::{Deref, DerefMut},
   7    path::{Path, PathBuf},
   8    rc::{Rc, Weak},
   9    sync::{Arc, atomic::Ordering::SeqCst},
  10    time::{Duration, Instant},
  11};
  12
  13use anyhow::{Context as _, Result, anyhow};
  14use derive_more::{Deref, DerefMut};
  15use futures::{
  16    Future, FutureExt,
  17    channel::oneshot,
  18    future::{LocalBoxFuture, Shared},
  19};
  20use itertools::Itertools;
  21use parking_lot::RwLock;
  22use slotmap::SlotMap;
  23
  24pub use async_context::*;
  25use collections::{FxHashMap, FxHashSet, HashMap, VecDeque};
  26pub use context::*;
  27pub use entity_map::*;
  28use http_client::{HttpClient, Url};
  29use smallvec::SmallVec;
  30#[cfg(any(test, feature = "test-support"))]
  31pub use test_context::*;
  32use util::{ResultExt, debug_panic};
  33#[cfg(all(target_os = "macos", any(test, feature = "test-support")))]
  34pub use visual_test_context::*;
  35
  36#[cfg(any(feature = "inspector", debug_assertions))]
  37use crate::InspectorElementRegistry;
  38use crate::{
  39    Action, ActionBuildError, ActionRegistry, Any, AnyView, AnyWindowHandle, AppContext, Arena,
  40    Asset, AssetSource, BackgroundExecutor, Bounds, ClipboardItem, CursorStyle, DispatchPhase,
  41    DisplayId, EventEmitter, FocusHandle, FocusMap, ForegroundExecutor, Global, KeyBinding,
  42    KeyContext, Keymap, Keystroke, LayoutId, Menu, MenuItem, OwnedMenu, PathPromptOptions, Pixels,
  43    Platform, PlatformDisplay, PlatformKeyboardLayout, PlatformKeyboardMapper, Point, Priority,
  44    PromptBuilder, PromptButton, PromptHandle, PromptLevel, Render, RenderImage,
  45    RenderablePromptHandle, Reservation, ScreenCaptureSource, SharedString, SubscriberSet,
  46    Subscription, SvgRenderer, Task, TextRenderingMode, TextSystem, ThermalState, Window,
  47    WindowAppearance, WindowHandle, WindowId, WindowInvalidator,
  48    colors::{Colors, GlobalColors},
  49    current_platform, hash, init_app_menus,
  50};
  51
  52mod async_context;
  53mod context;
  54mod entity_map;
  55#[cfg(any(test, feature = "test-support"))]
  56mod test_context;
  57#[cfg(all(target_os = "macos", any(test, feature = "test-support")))]
  58mod visual_test_context;
  59
  60/// The duration for which futures returned from [Context::on_app_quit] can run before the application fully quits.
  61pub const SHUTDOWN_TIMEOUT: Duration = Duration::from_millis(100);
  62
  63/// Temporary(?) wrapper around [`RefCell<App>`] to help us debug any double borrows.
  64/// Strongly consider removing after stabilization.
  65#[doc(hidden)]
  66pub struct AppCell {
  67    app: RefCell<App>,
  68}
  69
  70impl AppCell {
  71    #[doc(hidden)]
  72    #[track_caller]
  73    pub fn borrow(&self) -> AppRef<'_> {
  74        if option_env!("TRACK_THREAD_BORROWS").is_some() {
  75            let thread_id = std::thread::current().id();
  76            eprintln!("borrowed {thread_id:?}");
  77        }
  78        AppRef(self.app.borrow())
  79    }
  80
  81    #[doc(hidden)]
  82    #[track_caller]
  83    pub fn borrow_mut(&self) -> AppRefMut<'_> {
  84        if option_env!("TRACK_THREAD_BORROWS").is_some() {
  85            let thread_id = std::thread::current().id();
  86            eprintln!("borrowed {thread_id:?}");
  87        }
  88        AppRefMut(self.app.borrow_mut())
  89    }
  90
  91    #[doc(hidden)]
  92    #[track_caller]
  93    pub fn try_borrow_mut(&self) -> Result<AppRefMut<'_>, BorrowMutError> {
  94        if option_env!("TRACK_THREAD_BORROWS").is_some() {
  95            let thread_id = std::thread::current().id();
  96            eprintln!("borrowed {thread_id:?}");
  97        }
  98        Ok(AppRefMut(self.app.try_borrow_mut()?))
  99    }
 100}
 101
 102#[doc(hidden)]
 103#[derive(Deref, DerefMut)]
 104pub struct AppRef<'a>(Ref<'a, App>);
 105
 106impl Drop for AppRef<'_> {
 107    fn drop(&mut self) {
 108        if option_env!("TRACK_THREAD_BORROWS").is_some() {
 109            let thread_id = std::thread::current().id();
 110            eprintln!("dropped borrow from {thread_id:?}");
 111        }
 112    }
 113}
 114
 115#[doc(hidden)]
 116#[derive(Deref, DerefMut)]
 117pub struct AppRefMut<'a>(RefMut<'a, App>);
 118
 119impl Drop for AppRefMut<'_> {
 120    fn drop(&mut self) {
 121        if option_env!("TRACK_THREAD_BORROWS").is_some() {
 122            let thread_id = std::thread::current().id();
 123            eprintln!("dropped {thread_id:?}");
 124        }
 125    }
 126}
 127
 128/// A reference to a GPUI application, typically constructed in the `main` function of your app.
 129/// You won't interact with this type much outside of initial configuration and startup.
 130pub struct Application(Rc<AppCell>);
 131
 132/// Represents an application before it is fully launched. Once your app is
 133/// configured, you'll start the app with `App::run`.
 134impl Application {
 135    /// Builds an app with the given asset source.
 136    #[allow(clippy::new_without_default)]
 137    pub fn new() -> Self {
 138        #[cfg(any(test, feature = "test-support"))]
 139        log::info!("GPUI was compiled in test mode");
 140
 141        Self(App::new_app(
 142            current_platform(false),
 143            Arc::new(()),
 144            Arc::new(NullHttpClient),
 145        ))
 146    }
 147
 148    /// Build an app in headless mode. This prevents opening windows,
 149    /// but makes it possible to run an application in an context like
 150    /// SSH, where GUI applications are not allowed.
 151    pub fn headless() -> Self {
 152        Self(App::new_app(
 153            current_platform(true),
 154            Arc::new(()),
 155            Arc::new(NullHttpClient),
 156        ))
 157    }
 158
 159    /// Assigns the source of assets for the application.
 160    pub fn with_assets(self, asset_source: impl AssetSource) -> Self {
 161        let mut context_lock = self.0.borrow_mut();
 162        let asset_source = Arc::new(asset_source);
 163        context_lock.asset_source = asset_source.clone();
 164        context_lock.svg_renderer = SvgRenderer::new(asset_source);
 165        drop(context_lock);
 166        self
 167    }
 168
 169    /// Sets the HTTP client for the application.
 170    pub fn with_http_client(self, http_client: Arc<dyn HttpClient>) -> Self {
 171        let mut context_lock = self.0.borrow_mut();
 172        context_lock.http_client = http_client;
 173        drop(context_lock);
 174        self
 175    }
 176
 177    /// Configures when the application should automatically quit.
 178    /// By default, [`QuitMode::Default`] is used.
 179    pub fn with_quit_mode(self, mode: QuitMode) -> Self {
 180        self.0.borrow_mut().quit_mode = mode;
 181        self
 182    }
 183
 184    /// Start the application. The provided callback will be called once the
 185    /// app is fully launched.
 186    pub fn run<F>(self, on_finish_launching: F)
 187    where
 188        F: 'static + FnOnce(&mut App),
 189    {
 190        let this = self.0.clone();
 191        let platform = self.0.borrow().platform.clone();
 192        platform.run(Box::new(move || {
 193            let cx = &mut *this.borrow_mut();
 194            on_finish_launching(cx);
 195        }));
 196    }
 197
 198    /// Register a handler to be invoked when the platform instructs the application
 199    /// to open one or more URLs.
 200    pub fn on_open_urls<F>(&self, mut callback: F) -> &Self
 201    where
 202        F: 'static + FnMut(Vec<String>),
 203    {
 204        self.0.borrow().platform.on_open_urls(Box::new(callback));
 205        self
 206    }
 207
 208    /// Invokes a handler when an already-running application is launched.
 209    /// On macOS, this can occur when the application icon is double-clicked or the app is launched via the dock.
 210    pub fn on_reopen<F>(&self, mut callback: F) -> &Self
 211    where
 212        F: 'static + FnMut(&mut App),
 213    {
 214        let this = Rc::downgrade(&self.0);
 215        self.0.borrow_mut().platform.on_reopen(Box::new(move || {
 216            if let Some(app) = this.upgrade() {
 217                callback(&mut app.borrow_mut());
 218            }
 219        }));
 220        self
 221    }
 222
 223    /// Returns a handle to the [`BackgroundExecutor`] associated with this app, which can be used to spawn futures in the background.
 224    pub fn background_executor(&self) -> BackgroundExecutor {
 225        self.0.borrow().background_executor.clone()
 226    }
 227
 228    /// Returns a handle to the [`ForegroundExecutor`] associated with this app, which can be used to spawn futures in the foreground.
 229    pub fn foreground_executor(&self) -> ForegroundExecutor {
 230        self.0.borrow().foreground_executor.clone()
 231    }
 232
 233    /// Returns a reference to the [`TextSystem`] associated with this app.
 234    pub fn text_system(&self) -> Arc<TextSystem> {
 235        self.0.borrow().text_system.clone()
 236    }
 237
 238    /// Returns the file URL of the executable with the specified name in the application bundle
 239    pub fn path_for_auxiliary_executable(&self, name: &str) -> Result<PathBuf> {
 240        self.0.borrow().path_for_auxiliary_executable(name)
 241    }
 242}
 243
 244type Handler = Box<dyn FnMut(&mut App) -> bool + 'static>;
 245type Listener = Box<dyn FnMut(&dyn Any, &mut App) -> bool + 'static>;
 246pub(crate) type KeystrokeObserver =
 247    Box<dyn FnMut(&KeystrokeEvent, &mut Window, &mut App) -> bool + 'static>;
 248type QuitHandler = Box<dyn FnOnce(&mut App) -> LocalBoxFuture<'static, ()> + 'static>;
 249type WindowClosedHandler = Box<dyn FnMut(&mut App)>;
 250type ReleaseListener = Box<dyn FnOnce(&mut dyn Any, &mut App) + 'static>;
 251type NewEntityListener = Box<dyn FnMut(AnyEntity, &mut Option<&mut Window>, &mut App) + 'static>;
 252
 253/// Defines when the application should automatically quit.
 254#[derive(Debug, Clone, Copy, PartialEq, Eq, Default)]
 255pub enum QuitMode {
 256    /// Use [`QuitMode::Explicit`] on macOS and [`QuitMode::LastWindowClosed`] on other platforms.
 257    #[default]
 258    Default,
 259    /// Quit automatically when the last window is closed.
 260    LastWindowClosed,
 261    /// Quit only when requested via [`App::quit`].
 262    Explicit,
 263}
 264
 265#[doc(hidden)]
 266#[derive(Clone, PartialEq, Eq)]
 267pub struct SystemWindowTab {
 268    pub id: WindowId,
 269    pub title: SharedString,
 270    pub handle: AnyWindowHandle,
 271    pub last_active_at: Instant,
 272}
 273
 274impl SystemWindowTab {
 275    /// Create a new instance of the window tab.
 276    pub fn new(title: SharedString, handle: AnyWindowHandle) -> Self {
 277        Self {
 278            id: handle.id,
 279            title,
 280            handle,
 281            last_active_at: Instant::now(),
 282        }
 283    }
 284}
 285
 286/// A controller for managing window tabs.
 287#[derive(Default)]
 288pub struct SystemWindowTabController {
 289    visible: Option<bool>,
 290    tab_groups: FxHashMap<usize, Vec<SystemWindowTab>>,
 291}
 292
 293impl Global for SystemWindowTabController {}
 294
 295impl SystemWindowTabController {
 296    /// Create a new instance of the window tab controller.
 297    pub fn new() -> Self {
 298        Self {
 299            visible: None,
 300            tab_groups: FxHashMap::default(),
 301        }
 302    }
 303
 304    /// Initialize the global window tab controller.
 305    pub fn init(cx: &mut App) {
 306        cx.set_global(SystemWindowTabController::new());
 307    }
 308
 309    /// Get all tab groups.
 310    pub fn tab_groups(&self) -> &FxHashMap<usize, Vec<SystemWindowTab>> {
 311        &self.tab_groups
 312    }
 313
 314    /// Get the next tab group window handle.
 315    pub fn get_next_tab_group_window(cx: &mut App, id: WindowId) -> Option<&AnyWindowHandle> {
 316        let controller = cx.global::<SystemWindowTabController>();
 317        let current_group = controller
 318            .tab_groups
 319            .iter()
 320            .find_map(|(group, tabs)| tabs.iter().find(|tab| tab.id == id).map(|_| group));
 321
 322        let current_group = current_group?;
 323        // TODO: `.keys()` returns arbitrary order, what does "next" mean?
 324        let mut group_ids: Vec<_> = controller.tab_groups.keys().collect();
 325        let idx = group_ids.iter().position(|g| *g == current_group)?;
 326        let next_idx = (idx + 1) % group_ids.len();
 327
 328        controller
 329            .tab_groups
 330            .get(group_ids[next_idx])
 331            .and_then(|tabs| {
 332                tabs.iter()
 333                    .max_by_key(|tab| tab.last_active_at)
 334                    .or_else(|| tabs.first())
 335                    .map(|tab| &tab.handle)
 336            })
 337    }
 338
 339    /// Get the previous tab group window handle.
 340    pub fn get_prev_tab_group_window(cx: &mut App, id: WindowId) -> Option<&AnyWindowHandle> {
 341        let controller = cx.global::<SystemWindowTabController>();
 342        let current_group = controller
 343            .tab_groups
 344            .iter()
 345            .find_map(|(group, tabs)| tabs.iter().find(|tab| tab.id == id).map(|_| group));
 346
 347        let current_group = current_group?;
 348        // TODO: `.keys()` returns arbitrary order, what does "previous" mean?
 349        let mut group_ids: Vec<_> = controller.tab_groups.keys().collect();
 350        let idx = group_ids.iter().position(|g| *g == current_group)?;
 351        let prev_idx = if idx == 0 {
 352            group_ids.len() - 1
 353        } else {
 354            idx - 1
 355        };
 356
 357        controller
 358            .tab_groups
 359            .get(group_ids[prev_idx])
 360            .and_then(|tabs| {
 361                tabs.iter()
 362                    .max_by_key(|tab| tab.last_active_at)
 363                    .or_else(|| tabs.first())
 364                    .map(|tab| &tab.handle)
 365            })
 366    }
 367
 368    /// Get all tabs in the same window.
 369    pub fn tabs(&self, id: WindowId) -> Option<&Vec<SystemWindowTab>> {
 370        self.tab_groups
 371            .values()
 372            .find(|tabs| tabs.iter().any(|tab| tab.id == id))
 373    }
 374
 375    /// Initialize the visibility of the system window tab controller.
 376    pub fn init_visible(cx: &mut App, visible: bool) {
 377        let mut controller = cx.global_mut::<SystemWindowTabController>();
 378        if controller.visible.is_none() {
 379            controller.visible = Some(visible);
 380        }
 381    }
 382
 383    /// Get the visibility of the system window tab controller.
 384    pub fn is_visible(&self) -> bool {
 385        self.visible.unwrap_or(false)
 386    }
 387
 388    /// Set the visibility of the system window tab controller.
 389    pub fn set_visible(cx: &mut App, visible: bool) {
 390        let mut controller = cx.global_mut::<SystemWindowTabController>();
 391        controller.visible = Some(visible);
 392    }
 393
 394    /// Update the last active of a window.
 395    pub fn update_last_active(cx: &mut App, id: WindowId) {
 396        let mut controller = cx.global_mut::<SystemWindowTabController>();
 397        for windows in controller.tab_groups.values_mut() {
 398            for tab in windows.iter_mut() {
 399                if tab.id == id {
 400                    tab.last_active_at = Instant::now();
 401                }
 402            }
 403        }
 404    }
 405
 406    /// Update the position of a tab within its group.
 407    pub fn update_tab_position(cx: &mut App, id: WindowId, ix: usize) {
 408        let mut controller = cx.global_mut::<SystemWindowTabController>();
 409        for (_, windows) in controller.tab_groups.iter_mut() {
 410            if let Some(current_pos) = windows.iter().position(|tab| tab.id == id) {
 411                if ix < windows.len() && current_pos != ix {
 412                    let window_tab = windows.remove(current_pos);
 413                    windows.insert(ix, window_tab);
 414                }
 415                break;
 416            }
 417        }
 418    }
 419
 420    /// Update the title of a tab.
 421    pub fn update_tab_title(cx: &mut App, id: WindowId, title: SharedString) {
 422        let controller = cx.global::<SystemWindowTabController>();
 423        let tab = controller
 424            .tab_groups
 425            .values()
 426            .flat_map(|windows| windows.iter())
 427            .find(|tab| tab.id == id);
 428
 429        if tab.map_or(true, |t| t.title == title) {
 430            return;
 431        }
 432
 433        let mut controller = cx.global_mut::<SystemWindowTabController>();
 434        for windows in controller.tab_groups.values_mut() {
 435            for tab in windows.iter_mut() {
 436                if tab.id == id {
 437                    tab.title = title;
 438                    return;
 439                }
 440            }
 441        }
 442    }
 443
 444    /// Insert a tab into a tab group.
 445    pub fn add_tab(cx: &mut App, id: WindowId, tabs: Vec<SystemWindowTab>) {
 446        let mut controller = cx.global_mut::<SystemWindowTabController>();
 447        let Some(tab) = tabs.iter().find(|tab| tab.id == id).cloned() else {
 448            return;
 449        };
 450
 451        let mut expected_tab_ids: Vec<_> = tabs
 452            .iter()
 453            .filter(|tab| tab.id != id)
 454            .map(|tab| tab.id)
 455            .sorted()
 456            .collect();
 457
 458        let mut tab_group_id = None;
 459        for (group_id, group_tabs) in &controller.tab_groups {
 460            let tab_ids: Vec<_> = group_tabs.iter().map(|tab| tab.id).sorted().collect();
 461            if tab_ids == expected_tab_ids {
 462                tab_group_id = Some(*group_id);
 463                break;
 464            }
 465        }
 466
 467        if let Some(tab_group_id) = tab_group_id {
 468            if let Some(tabs) = controller.tab_groups.get_mut(&tab_group_id) {
 469                tabs.push(tab);
 470            }
 471        } else {
 472            let new_group_id = controller.tab_groups.len();
 473            controller.tab_groups.insert(new_group_id, tabs);
 474        }
 475    }
 476
 477    /// Remove a tab from a tab group.
 478    pub fn remove_tab(cx: &mut App, id: WindowId) -> Option<SystemWindowTab> {
 479        let mut controller = cx.global_mut::<SystemWindowTabController>();
 480        let mut removed_tab = None;
 481
 482        controller.tab_groups.retain(|_, tabs| {
 483            if let Some(pos) = tabs.iter().position(|tab| tab.id == id) {
 484                removed_tab = Some(tabs.remove(pos));
 485            }
 486            !tabs.is_empty()
 487        });
 488
 489        removed_tab
 490    }
 491
 492    /// Move a tab to a new tab group.
 493    pub fn move_tab_to_new_window(cx: &mut App, id: WindowId) {
 494        let mut removed_tab = Self::remove_tab(cx, id);
 495        let mut controller = cx.global_mut::<SystemWindowTabController>();
 496
 497        if let Some(tab) = removed_tab {
 498            let new_group_id = controller.tab_groups.keys().max().map_or(0, |k| k + 1);
 499            controller.tab_groups.insert(new_group_id, vec![tab]);
 500        }
 501    }
 502
 503    /// Merge all tab groups into a single group.
 504    pub fn merge_all_windows(cx: &mut App, id: WindowId) {
 505        let mut controller = cx.global_mut::<SystemWindowTabController>();
 506        let Some(initial_tabs) = controller.tabs(id) else {
 507            return;
 508        };
 509
 510        let initial_tabs_len = initial_tabs.len();
 511        let mut all_tabs = initial_tabs.clone();
 512
 513        for (_, mut tabs) in controller.tab_groups.drain() {
 514            tabs.retain(|tab| !all_tabs[..initial_tabs_len].contains(tab));
 515            all_tabs.extend(tabs);
 516        }
 517
 518        controller.tab_groups.insert(0, all_tabs);
 519    }
 520
 521    /// Selects the next tab in the tab group in the trailing direction.
 522    pub fn select_next_tab(cx: &mut App, id: WindowId) {
 523        let mut controller = cx.global_mut::<SystemWindowTabController>();
 524        let Some(tabs) = controller.tabs(id) else {
 525            return;
 526        };
 527
 528        let current_index = tabs.iter().position(|tab| tab.id == id).unwrap();
 529        let next_index = (current_index + 1) % tabs.len();
 530
 531        let _ = &tabs[next_index].handle.update(cx, |_, window, _| {
 532            window.activate_window();
 533        });
 534    }
 535
 536    /// Selects the previous tab in the tab group in the leading direction.
 537    pub fn select_previous_tab(cx: &mut App, id: WindowId) {
 538        let mut controller = cx.global_mut::<SystemWindowTabController>();
 539        let Some(tabs) = controller.tabs(id) else {
 540            return;
 541        };
 542
 543        let current_index = tabs.iter().position(|tab| tab.id == id).unwrap();
 544        let previous_index = if current_index == 0 {
 545            tabs.len() - 1
 546        } else {
 547            current_index - 1
 548        };
 549
 550        let _ = &tabs[previous_index].handle.update(cx, |_, window, _| {
 551            window.activate_window();
 552        });
 553    }
 554}
 555
 556pub(crate) enum GpuiMode {
 557    #[cfg(any(test, feature = "test-support"))]
 558    Test {
 559        skip_drawing: bool,
 560    },
 561    Production,
 562}
 563
 564impl GpuiMode {
 565    #[cfg(any(test, feature = "test-support"))]
 566    pub fn test() -> Self {
 567        GpuiMode::Test {
 568            skip_drawing: false,
 569        }
 570    }
 571
 572    #[inline]
 573    pub(crate) fn skip_drawing(&self) -> bool {
 574        match self {
 575            #[cfg(any(test, feature = "test-support"))]
 576            GpuiMode::Test { skip_drawing } => *skip_drawing,
 577            GpuiMode::Production => false,
 578        }
 579    }
 580}
 581
 582/// Contains the state of the full application, and passed as a reference to a variety of callbacks.
 583/// Other [Context] derefs to this type.
 584/// You need a reference to an `App` to access the state of a [Entity].
 585pub struct App {
 586    pub(crate) this: Weak<AppCell>,
 587    pub(crate) platform: Rc<dyn Platform>,
 588    pub(crate) mode: GpuiMode,
 589    text_system: Arc<TextSystem>,
 590    flushing_effects: bool,
 591    pending_updates: usize,
 592    pub(crate) actions: Rc<ActionRegistry>,
 593    pub(crate) active_drag: Option<AnyDrag>,
 594    pub(crate) background_executor: BackgroundExecutor,
 595    pub(crate) foreground_executor: ForegroundExecutor,
 596    pub(crate) loading_assets: FxHashMap<(TypeId, u64), Box<dyn Any>>,
 597    asset_source: Arc<dyn AssetSource>,
 598    pub(crate) svg_renderer: SvgRenderer,
 599    http_client: Arc<dyn HttpClient>,
 600    pub(crate) globals_by_type: FxHashMap<TypeId, Box<dyn Any>>,
 601    pub(crate) entities: EntityMap,
 602    pub(crate) window_update_stack: Vec<WindowId>,
 603    pub(crate) new_entity_observers: SubscriberSet<TypeId, NewEntityListener>,
 604    pub(crate) windows: SlotMap<WindowId, Option<Box<Window>>>,
 605    pub(crate) window_handles: FxHashMap<WindowId, AnyWindowHandle>,
 606    pub(crate) focus_handles: Arc<FocusMap>,
 607    pub(crate) keymap: Rc<RefCell<Keymap>>,
 608    pub(crate) keyboard_layout: Box<dyn PlatformKeyboardLayout>,
 609    pub(crate) keyboard_mapper: Rc<dyn PlatformKeyboardMapper>,
 610    pub(crate) global_action_listeners:
 611        FxHashMap<TypeId, Vec<Rc<dyn Fn(&dyn Any, DispatchPhase, &mut Self)>>>,
 612    pending_effects: VecDeque<Effect>,
 613    pub(crate) pending_notifications: FxHashSet<EntityId>,
 614    pub(crate) pending_global_notifications: FxHashSet<TypeId>,
 615    pub(crate) observers: SubscriberSet<EntityId, Handler>,
 616    // TypeId is the type of the event that the listener callback expects
 617    pub(crate) event_listeners: SubscriberSet<EntityId, (TypeId, Listener)>,
 618    pub(crate) keystroke_observers: SubscriberSet<(), KeystrokeObserver>,
 619    pub(crate) keystroke_interceptors: SubscriberSet<(), KeystrokeObserver>,
 620    pub(crate) keyboard_layout_observers: SubscriberSet<(), Handler>,
 621    pub(crate) thermal_state_observers: SubscriberSet<(), Handler>,
 622    pub(crate) release_listeners: SubscriberSet<EntityId, ReleaseListener>,
 623    pub(crate) global_observers: SubscriberSet<TypeId, Handler>,
 624    pub(crate) quit_observers: SubscriberSet<(), QuitHandler>,
 625    pub(crate) restart_observers: SubscriberSet<(), Handler>,
 626    pub(crate) restart_path: Option<PathBuf>,
 627    pub(crate) window_closed_observers: SubscriberSet<(), WindowClosedHandler>,
 628    pub(crate) layout_id_buffer: Vec<LayoutId>, // We recycle this memory across layout requests.
 629    pub(crate) propagate_event: bool,
 630    pub(crate) prompt_builder: Option<PromptBuilder>,
 631    pub(crate) window_invalidators_by_entity:
 632        FxHashMap<EntityId, FxHashMap<WindowId, WindowInvalidator>>,
 633    pub(crate) tracked_entities: FxHashMap<WindowId, FxHashSet<EntityId>>,
 634    #[cfg(any(feature = "inspector", debug_assertions))]
 635    pub(crate) inspector_renderer: Option<crate::InspectorRenderer>,
 636    #[cfg(any(feature = "inspector", debug_assertions))]
 637    pub(crate) inspector_element_registry: InspectorElementRegistry,
 638    #[cfg(any(test, feature = "test-support", debug_assertions))]
 639    pub(crate) name: Option<&'static str>,
 640    pub(crate) text_rendering_mode: Rc<Cell<TextRenderingMode>>,
 641    quit_mode: QuitMode,
 642    quitting: bool,
 643    /// Per-App element arena. This isolates element allocations between different
 644    /// App instances (important for tests where multiple Apps run concurrently).
 645    pub(crate) element_arena: RefCell<Arena>,
 646}
 647
 648impl App {
 649    #[allow(clippy::new_ret_no_self)]
 650    pub(crate) fn new_app(
 651        platform: Rc<dyn Platform>,
 652        asset_source: Arc<dyn AssetSource>,
 653        http_client: Arc<dyn HttpClient>,
 654    ) -> Rc<AppCell> {
 655        let background_executor = platform.background_executor();
 656        let foreground_executor = platform.foreground_executor();
 657        assert!(
 658            background_executor.is_main_thread(),
 659            "must construct App on main thread"
 660        );
 661
 662        let text_system = Arc::new(TextSystem::new(platform.text_system()));
 663        let entities = EntityMap::new();
 664        let keyboard_layout = platform.keyboard_layout();
 665        let keyboard_mapper = platform.keyboard_mapper();
 666
 667        let app = Rc::new_cyclic(|this| AppCell {
 668            app: RefCell::new(App {
 669                this: this.clone(),
 670                platform: platform.clone(),
 671                text_system,
 672                text_rendering_mode: Rc::new(Cell::new(TextRenderingMode::default())),
 673                mode: GpuiMode::Production,
 674                actions: Rc::new(ActionRegistry::default()),
 675                flushing_effects: false,
 676                pending_updates: 0,
 677                active_drag: None,
 678                background_executor,
 679                foreground_executor,
 680                svg_renderer: SvgRenderer::new(asset_source.clone()),
 681                loading_assets: Default::default(),
 682                asset_source,
 683                http_client,
 684                globals_by_type: FxHashMap::default(),
 685                entities,
 686                new_entity_observers: SubscriberSet::new(),
 687                windows: SlotMap::with_key(),
 688                window_update_stack: Vec::new(),
 689                window_handles: FxHashMap::default(),
 690                focus_handles: Arc::new(RwLock::new(SlotMap::with_key())),
 691                keymap: Rc::new(RefCell::new(Keymap::default())),
 692                keyboard_layout,
 693                keyboard_mapper,
 694                global_action_listeners: FxHashMap::default(),
 695                pending_effects: VecDeque::new(),
 696                pending_notifications: FxHashSet::default(),
 697                pending_global_notifications: FxHashSet::default(),
 698                observers: SubscriberSet::new(),
 699                tracked_entities: FxHashMap::default(),
 700                window_invalidators_by_entity: FxHashMap::default(),
 701                event_listeners: SubscriberSet::new(),
 702                release_listeners: SubscriberSet::new(),
 703                keystroke_observers: SubscriberSet::new(),
 704                keystroke_interceptors: SubscriberSet::new(),
 705                keyboard_layout_observers: SubscriberSet::new(),
 706                thermal_state_observers: SubscriberSet::new(),
 707                global_observers: SubscriberSet::new(),
 708                quit_observers: SubscriberSet::new(),
 709                restart_observers: SubscriberSet::new(),
 710                restart_path: None,
 711                window_closed_observers: SubscriberSet::new(),
 712                layout_id_buffer: Default::default(),
 713                propagate_event: true,
 714                prompt_builder: Some(PromptBuilder::Default),
 715                #[cfg(any(feature = "inspector", debug_assertions))]
 716                inspector_renderer: None,
 717                #[cfg(any(feature = "inspector", debug_assertions))]
 718                inspector_element_registry: InspectorElementRegistry::default(),
 719                quit_mode: QuitMode::default(),
 720                quitting: false,
 721
 722                #[cfg(any(test, feature = "test-support", debug_assertions))]
 723                name: None,
 724                element_arena: RefCell::new(Arena::new(1024 * 1024)),
 725            }),
 726        });
 727
 728        init_app_menus(platform.as_ref(), &app.borrow());
 729        SystemWindowTabController::init(&mut app.borrow_mut());
 730
 731        platform.on_keyboard_layout_change(Box::new({
 732            let app = Rc::downgrade(&app);
 733            move || {
 734                if let Some(app) = app.upgrade() {
 735                    let cx = &mut app.borrow_mut();
 736                    cx.keyboard_layout = cx.platform.keyboard_layout();
 737                    cx.keyboard_mapper = cx.platform.keyboard_mapper();
 738                    cx.keyboard_layout_observers
 739                        .clone()
 740                        .retain(&(), move |callback| (callback)(cx));
 741                }
 742            }
 743        }));
 744
 745        platform.on_thermal_state_change(Box::new({
 746            let app = Rc::downgrade(&app);
 747            move || {
 748                if let Some(app) = app.upgrade() {
 749                    let cx = &mut app.borrow_mut();
 750                    cx.thermal_state_observers
 751                        .clone()
 752                        .retain(&(), move |callback| (callback)(cx));
 753                }
 754            }
 755        }));
 756
 757        platform.on_quit(Box::new({
 758            let cx = app.clone();
 759            move || {
 760                cx.borrow_mut().shutdown();
 761            }
 762        }));
 763
 764        app
 765    }
 766
 767    /// Quit the application gracefully. Handlers registered with [`Context::on_app_quit`]
 768    /// will be given 100ms to complete before exiting.
 769    pub fn shutdown(&mut self) {
 770        let mut futures = Vec::new();
 771
 772        for observer in self.quit_observers.remove(&()) {
 773            futures.push(observer(self));
 774        }
 775
 776        self.windows.clear();
 777        self.window_handles.clear();
 778        self.flush_effects();
 779        self.quitting = true;
 780
 781        let futures = futures::future::join_all(futures);
 782        if self
 783            .foreground_executor
 784            .block_with_timeout(SHUTDOWN_TIMEOUT, futures)
 785            .is_err()
 786        {
 787            log::error!("timed out waiting on app_will_quit");
 788        }
 789
 790        self.quitting = false;
 791    }
 792
 793    /// Get the id of the current keyboard layout
 794    pub fn keyboard_layout(&self) -> &dyn PlatformKeyboardLayout {
 795        self.keyboard_layout.as_ref()
 796    }
 797
 798    /// Get the current keyboard mapper.
 799    pub fn keyboard_mapper(&self) -> &Rc<dyn PlatformKeyboardMapper> {
 800        &self.keyboard_mapper
 801    }
 802
 803    /// Invokes a handler when the current keyboard layout changes
 804    pub fn on_keyboard_layout_change<F>(&self, mut callback: F) -> Subscription
 805    where
 806        F: 'static + FnMut(&mut App),
 807    {
 808        let (subscription, activate) = self.keyboard_layout_observers.insert(
 809            (),
 810            Box::new(move |cx| {
 811                callback(cx);
 812                true
 813            }),
 814        );
 815        activate();
 816        subscription
 817    }
 818
 819    /// Gracefully quit the application via the platform's standard routine.
 820    pub fn quit(&self) {
 821        self.platform.quit();
 822    }
 823
 824    /// Schedules all windows in the application to be redrawn. This can be called
 825    /// multiple times in an update cycle and still result in a single redraw.
 826    pub fn refresh_windows(&mut self) {
 827        self.pending_effects.push_back(Effect::RefreshWindows);
 828    }
 829
 830    pub(crate) fn update<R>(&mut self, update: impl FnOnce(&mut Self) -> R) -> R {
 831        self.start_update();
 832        let result = update(self);
 833        self.finish_update();
 834        result
 835    }
 836
 837    pub(crate) fn start_update(&mut self) {
 838        self.pending_updates += 1;
 839    }
 840
 841    pub(crate) fn finish_update(&mut self) {
 842        if !self.flushing_effects && self.pending_updates == 1 {
 843            self.flushing_effects = true;
 844            self.flush_effects();
 845            self.flushing_effects = false;
 846        }
 847        self.pending_updates -= 1;
 848    }
 849
 850    /// Arrange a callback to be invoked when the given entity calls `notify` on its respective context.
 851    pub fn observe<W>(
 852        &mut self,
 853        entity: &Entity<W>,
 854        mut on_notify: impl FnMut(Entity<W>, &mut App) + 'static,
 855    ) -> Subscription
 856    where
 857        W: 'static,
 858    {
 859        self.observe_internal(entity, move |e, cx| {
 860            on_notify(e, cx);
 861            true
 862        })
 863    }
 864
 865    pub(crate) fn detect_accessed_entities<R>(
 866        &mut self,
 867        callback: impl FnOnce(&mut App) -> R,
 868    ) -> (R, FxHashSet<EntityId>) {
 869        let accessed_entities_start = self.entities.accessed_entities.borrow().clone();
 870        let result = callback(self);
 871        let accessed_entities_end = self.entities.accessed_entities.borrow().clone();
 872        let entities_accessed_in_callback = accessed_entities_end
 873            .difference(&accessed_entities_start)
 874            .copied()
 875            .collect::<FxHashSet<EntityId>>();
 876        (result, entities_accessed_in_callback)
 877    }
 878
 879    pub(crate) fn record_entities_accessed(
 880        &mut self,
 881        window_handle: AnyWindowHandle,
 882        invalidator: WindowInvalidator,
 883        entities: &FxHashSet<EntityId>,
 884    ) {
 885        let mut tracked_entities =
 886            std::mem::take(self.tracked_entities.entry(window_handle.id).or_default());
 887        for entity in tracked_entities.iter() {
 888            self.window_invalidators_by_entity
 889                .entry(*entity)
 890                .and_modify(|windows| {
 891                    windows.remove(&window_handle.id);
 892                });
 893        }
 894        for entity in entities.iter() {
 895            self.window_invalidators_by_entity
 896                .entry(*entity)
 897                .or_default()
 898                .insert(window_handle.id, invalidator.clone());
 899        }
 900        tracked_entities.clear();
 901        tracked_entities.extend(entities.iter().copied());
 902        self.tracked_entities
 903            .insert(window_handle.id, tracked_entities);
 904    }
 905
 906    pub(crate) fn new_observer(&mut self, key: EntityId, value: Handler) -> Subscription {
 907        let (subscription, activate) = self.observers.insert(key, value);
 908        self.defer(move |_| activate());
 909        subscription
 910    }
 911
 912    pub(crate) fn observe_internal<W>(
 913        &mut self,
 914        entity: &Entity<W>,
 915        mut on_notify: impl FnMut(Entity<W>, &mut App) -> bool + 'static,
 916    ) -> Subscription
 917    where
 918        W: 'static,
 919    {
 920        let entity_id = entity.entity_id();
 921        let handle = entity.downgrade();
 922        self.new_observer(
 923            entity_id,
 924            Box::new(move |cx| {
 925                if let Some(entity) = handle.upgrade() {
 926                    on_notify(entity, cx)
 927                } else {
 928                    false
 929                }
 930            }),
 931        )
 932    }
 933
 934    /// Arrange for the given callback to be invoked whenever the given entity emits an event of a given type.
 935    /// The callback is provided a handle to the emitting entity and a reference to the emitted event.
 936    pub fn subscribe<T, Event>(
 937        &mut self,
 938        entity: &Entity<T>,
 939        mut on_event: impl FnMut(Entity<T>, &Event, &mut App) + 'static,
 940    ) -> Subscription
 941    where
 942        T: 'static + EventEmitter<Event>,
 943        Event: 'static,
 944    {
 945        self.subscribe_internal(entity, move |entity, event, cx| {
 946            on_event(entity, event, cx);
 947            true
 948        })
 949    }
 950
 951    pub(crate) fn new_subscription(
 952        &mut self,
 953        key: EntityId,
 954        value: (TypeId, Listener),
 955    ) -> Subscription {
 956        let (subscription, activate) = self.event_listeners.insert(key, value);
 957        self.defer(move |_| activate());
 958        subscription
 959    }
 960    pub(crate) fn subscribe_internal<T, Evt>(
 961        &mut self,
 962        entity: &Entity<T>,
 963        mut on_event: impl FnMut(Entity<T>, &Evt, &mut App) -> bool + 'static,
 964    ) -> Subscription
 965    where
 966        T: 'static + EventEmitter<Evt>,
 967        Evt: 'static,
 968    {
 969        let entity_id = entity.entity_id();
 970        let handle = entity.downgrade();
 971        self.new_subscription(
 972            entity_id,
 973            (
 974                TypeId::of::<Evt>(),
 975                Box::new(move |event, cx| {
 976                    let event: &Evt = event.downcast_ref().expect("invalid event type");
 977                    if let Some(entity) = handle.upgrade() {
 978                        on_event(entity, event, cx)
 979                    } else {
 980                        false
 981                    }
 982                }),
 983            ),
 984        )
 985    }
 986
 987    /// Returns handles to all open windows in the application.
 988    /// Each handle could be downcast to a handle typed for the root view of that window.
 989    /// To find all windows of a given type, you could filter on
 990    pub fn windows(&self) -> Vec<AnyWindowHandle> {
 991        self.windows
 992            .keys()
 993            .flat_map(|window_id| self.window_handles.get(&window_id).copied())
 994            .collect()
 995    }
 996
 997    /// Returns the window handles ordered by their appearance on screen, front to back.
 998    ///
 999    /// The first window in the returned list is the active/topmost window of the application.
1000    ///
1001    /// This method returns None if the platform doesn't implement the method yet.
1002    pub fn window_stack(&self) -> Option<Vec<AnyWindowHandle>> {
1003        self.platform.window_stack()
1004    }
1005
1006    /// Returns a handle to the window that is currently focused at the platform level, if one exists.
1007    pub fn active_window(&self) -> Option<AnyWindowHandle> {
1008        self.platform.active_window()
1009    }
1010
1011    /// Opens a new window with the given option and the root view returned by the given function.
1012    /// The function is invoked with a `Window`, which can be used to interact with window-specific
1013    /// functionality.
1014    pub fn open_window<V: 'static + Render>(
1015        &mut self,
1016        options: crate::WindowOptions,
1017        build_root_view: impl FnOnce(&mut Window, &mut App) -> Entity<V>,
1018    ) -> anyhow::Result<WindowHandle<V>> {
1019        self.update(|cx| {
1020            let id = cx.windows.insert(None);
1021            let handle = WindowHandle::new(id);
1022            match Window::new(handle.into(), options, cx) {
1023                Ok(mut window) => {
1024                    cx.window_update_stack.push(id);
1025                    let root_view = build_root_view(&mut window, cx);
1026                    cx.window_update_stack.pop();
1027                    window.root.replace(root_view.into());
1028                    window.defer(cx, |window: &mut Window, cx| window.appearance_changed(cx));
1029
1030                    // allow a window to draw at least once before returning
1031                    // this didn't cause any issues on non windows platforms as it seems we always won the race to on_request_frame
1032                    // on windows we quite frequently lose the race and return a window that has never rendered, which leads to a crash
1033                    // where DispatchTree::root_node_id asserts on empty nodes
1034                    let clear = window.draw(cx);
1035                    clear.clear();
1036
1037                    cx.window_handles.insert(id, window.handle);
1038                    cx.windows.get_mut(id).unwrap().replace(Box::new(window));
1039                    Ok(handle)
1040                }
1041                Err(e) => {
1042                    cx.windows.remove(id);
1043                    Err(e)
1044                }
1045            }
1046        })
1047    }
1048
1049    /// Instructs the platform to activate the application by bringing it to the foreground.
1050    pub fn activate(&self, ignoring_other_apps: bool) {
1051        self.platform.activate(ignoring_other_apps);
1052    }
1053
1054    /// Hide the application at the platform level.
1055    pub fn hide(&self) {
1056        self.platform.hide();
1057    }
1058
1059    /// Hide other applications at the platform level.
1060    pub fn hide_other_apps(&self) {
1061        self.platform.hide_other_apps();
1062    }
1063
1064    /// Unhide other applications at the platform level.
1065    pub fn unhide_other_apps(&self) {
1066        self.platform.unhide_other_apps();
1067    }
1068
1069    /// Returns the list of currently active displays.
1070    pub fn displays(&self) -> Vec<Rc<dyn PlatformDisplay>> {
1071        self.platform.displays()
1072    }
1073
1074    /// Returns the primary display that will be used for new windows.
1075    pub fn primary_display(&self) -> Option<Rc<dyn PlatformDisplay>> {
1076        self.platform.primary_display()
1077    }
1078
1079    /// Returns whether `screen_capture_sources` may work.
1080    pub fn is_screen_capture_supported(&self) -> bool {
1081        self.platform.is_screen_capture_supported()
1082    }
1083
1084    /// Returns a list of available screen capture sources.
1085    pub fn screen_capture_sources(
1086        &self,
1087    ) -> oneshot::Receiver<Result<Vec<Rc<dyn ScreenCaptureSource>>>> {
1088        self.platform.screen_capture_sources()
1089    }
1090
1091    /// Returns the display with the given ID, if one exists.
1092    pub fn find_display(&self, id: DisplayId) -> Option<Rc<dyn PlatformDisplay>> {
1093        self.displays()
1094            .iter()
1095            .find(|display| display.id() == id)
1096            .cloned()
1097    }
1098
1099    /// Returns the current thermal state of the system.
1100    pub fn thermal_state(&self) -> ThermalState {
1101        self.platform.thermal_state()
1102    }
1103
1104    /// Invokes a handler when the thermal state changes
1105    pub fn on_thermal_state_change<F>(&self, mut callback: F) -> Subscription
1106    where
1107        F: 'static + FnMut(&mut App),
1108    {
1109        let (subscription, activate) = self.thermal_state_observers.insert(
1110            (),
1111            Box::new(move |cx| {
1112                callback(cx);
1113                true
1114            }),
1115        );
1116        activate();
1117        subscription
1118    }
1119
1120    /// Returns the appearance of the application's windows.
1121    pub fn window_appearance(&self) -> WindowAppearance {
1122        self.platform.window_appearance()
1123    }
1124
1125    /// Reads data from the platform clipboard.
1126    pub fn read_from_clipboard(&self) -> Option<ClipboardItem> {
1127        self.platform.read_from_clipboard()
1128    }
1129
1130    /// Sets the text rendering mode for the application.
1131    pub fn set_text_rendering_mode(&mut self, mode: TextRenderingMode) {
1132        self.text_rendering_mode.set(mode);
1133    }
1134
1135    /// Returns the current text rendering mode for the application.
1136    pub fn text_rendering_mode(&self) -> TextRenderingMode {
1137        self.text_rendering_mode.get()
1138    }
1139
1140    /// Writes data to the platform clipboard.
1141    pub fn write_to_clipboard(&self, item: ClipboardItem) {
1142        self.platform.write_to_clipboard(item)
1143    }
1144
1145    /// Reads data from the primary selection buffer.
1146    /// Only available on Linux.
1147    #[cfg(any(target_os = "linux", target_os = "freebsd"))]
1148    pub fn read_from_primary(&self) -> Option<ClipboardItem> {
1149        self.platform.read_from_primary()
1150    }
1151
1152    /// Writes data to the primary selection buffer.
1153    /// Only available on Linux.
1154    #[cfg(any(target_os = "linux", target_os = "freebsd"))]
1155    pub fn write_to_primary(&self, item: ClipboardItem) {
1156        self.platform.write_to_primary(item)
1157    }
1158
1159    /// Reads data from macOS's "Find" pasteboard.
1160    ///
1161    /// Used to share the current search string between apps.
1162    ///
1163    /// https://developer.apple.com/documentation/appkit/nspasteboard/name-swift.struct/find
1164    #[cfg(target_os = "macos")]
1165    pub fn read_from_find_pasteboard(&self) -> Option<ClipboardItem> {
1166        self.platform.read_from_find_pasteboard()
1167    }
1168
1169    /// Writes data to macOS's "Find" pasteboard.
1170    ///
1171    /// Used to share the current search string between apps.
1172    ///
1173    /// https://developer.apple.com/documentation/appkit/nspasteboard/name-swift.struct/find
1174    #[cfg(target_os = "macos")]
1175    pub fn write_to_find_pasteboard(&self, item: ClipboardItem) {
1176        self.platform.write_to_find_pasteboard(item)
1177    }
1178
1179    /// Writes credentials to the platform keychain.
1180    pub fn write_credentials(
1181        &self,
1182        url: &str,
1183        username: &str,
1184        password: &[u8],
1185    ) -> Task<Result<()>> {
1186        self.platform.write_credentials(url, username, password)
1187    }
1188
1189    /// Reads credentials from the platform keychain.
1190    pub fn read_credentials(&self, url: &str) -> Task<Result<Option<(String, Vec<u8>)>>> {
1191        self.platform.read_credentials(url)
1192    }
1193
1194    /// Deletes credentials from the platform keychain.
1195    pub fn delete_credentials(&self, url: &str) -> Task<Result<()>> {
1196        self.platform.delete_credentials(url)
1197    }
1198
1199    /// Directs the platform's default browser to open the given URL.
1200    pub fn open_url(&self, url: &str) {
1201        self.platform.open_url(url);
1202    }
1203
1204    /// Registers the given URL scheme (e.g. `zed` for `zed://` urls) to be
1205    /// opened by the current app.
1206    ///
1207    /// On some platforms (e.g. macOS) you may be able to register URL schemes
1208    /// as part of app distribution, but this method exists to let you register
1209    /// schemes at runtime.
1210    pub fn register_url_scheme(&self, scheme: &str) -> Task<Result<()>> {
1211        self.platform.register_url_scheme(scheme)
1212    }
1213
1214    /// Returns the full pathname of the current app bundle.
1215    ///
1216    /// Returns an error if the app is not being run from a bundle.
1217    pub fn app_path(&self) -> Result<PathBuf> {
1218        self.platform.app_path()
1219    }
1220
1221    /// On Linux, returns the name of the compositor in use.
1222    ///
1223    /// Returns an empty string on other platforms.
1224    pub fn compositor_name(&self) -> &'static str {
1225        self.platform.compositor_name()
1226    }
1227
1228    /// Returns the file URL of the executable with the specified name in the application bundle
1229    pub fn path_for_auxiliary_executable(&self, name: &str) -> Result<PathBuf> {
1230        self.platform.path_for_auxiliary_executable(name)
1231    }
1232
1233    /// Displays a platform modal for selecting paths.
1234    ///
1235    /// When one or more paths are selected, they'll be relayed asynchronously via the returned oneshot channel.
1236    /// If cancelled, a `None` will be relayed instead.
1237    /// May return an error on Linux if the file picker couldn't be opened.
1238    pub fn prompt_for_paths(
1239        &self,
1240        options: PathPromptOptions,
1241    ) -> oneshot::Receiver<Result<Option<Vec<PathBuf>>>> {
1242        self.platform.prompt_for_paths(options)
1243    }
1244
1245    /// Displays a platform modal for selecting a new path where a file can be saved.
1246    ///
1247    /// The provided directory will be used to set the initial location.
1248    /// When a path is selected, it is relayed asynchronously via the returned oneshot channel.
1249    /// If cancelled, a `None` will be relayed instead.
1250    /// May return an error on Linux if the file picker couldn't be opened.
1251    pub fn prompt_for_new_path(
1252        &self,
1253        directory: &Path,
1254        suggested_name: Option<&str>,
1255    ) -> oneshot::Receiver<Result<Option<PathBuf>>> {
1256        self.platform.prompt_for_new_path(directory, suggested_name)
1257    }
1258
1259    /// Reveals the specified path at the platform level, such as in Finder on macOS.
1260    pub fn reveal_path(&self, path: &Path) {
1261        self.platform.reveal_path(path)
1262    }
1263
1264    /// Opens the specified path with the system's default application.
1265    pub fn open_with_system(&self, path: &Path) {
1266        self.platform.open_with_system(path)
1267    }
1268
1269    /// Returns whether the user has configured scrollbars to auto-hide at the platform level.
1270    pub fn should_auto_hide_scrollbars(&self) -> bool {
1271        self.platform.should_auto_hide_scrollbars()
1272    }
1273
1274    /// Restarts the application.
1275    pub fn restart(&mut self) {
1276        self.restart_observers
1277            .clone()
1278            .retain(&(), |observer| observer(self));
1279        self.platform.restart(self.restart_path.take())
1280    }
1281
1282    /// Sets the path to use when restarting the application.
1283    pub fn set_restart_path(&mut self, path: PathBuf) {
1284        self.restart_path = Some(path);
1285    }
1286
1287    /// Returns the HTTP client for the application.
1288    pub fn http_client(&self) -> Arc<dyn HttpClient> {
1289        self.http_client.clone()
1290    }
1291
1292    /// Sets the HTTP client for the application.
1293    pub fn set_http_client(&mut self, new_client: Arc<dyn HttpClient>) {
1294        self.http_client = new_client;
1295    }
1296
1297    /// Configures when the application should automatically quit.
1298    /// By default, [`QuitMode::Default`] is used.
1299    pub fn set_quit_mode(&mut self, mode: QuitMode) {
1300        self.quit_mode = mode;
1301    }
1302
1303    /// Returns the SVG renderer used by the application.
1304    pub fn svg_renderer(&self) -> SvgRenderer {
1305        self.svg_renderer.clone()
1306    }
1307
1308    pub(crate) fn push_effect(&mut self, effect: Effect) {
1309        match &effect {
1310            Effect::Notify { emitter } => {
1311                if !self.pending_notifications.insert(*emitter) {
1312                    return;
1313                }
1314            }
1315            Effect::NotifyGlobalObservers { global_type } => {
1316                if !self.pending_global_notifications.insert(*global_type) {
1317                    return;
1318                }
1319            }
1320            _ => {}
1321        };
1322
1323        self.pending_effects.push_back(effect);
1324    }
1325
1326    /// Called at the end of [`App::update`] to complete any side effects
1327    /// such as notifying observers, emitting events, etc. Effects can themselves
1328    /// cause effects, so we continue looping until all effects are processed.
1329    fn flush_effects(&mut self) {
1330        loop {
1331            self.release_dropped_entities();
1332            self.release_dropped_focus_handles();
1333            if let Some(effect) = self.pending_effects.pop_front() {
1334                match effect {
1335                    Effect::Notify { emitter } => {
1336                        self.apply_notify_effect(emitter);
1337                    }
1338
1339                    Effect::Emit {
1340                        emitter,
1341                        event_type,
1342                        event,
1343                    } => self.apply_emit_effect(emitter, event_type, event),
1344
1345                    Effect::RefreshWindows => {
1346                        self.apply_refresh_effect();
1347                    }
1348
1349                    Effect::NotifyGlobalObservers { global_type } => {
1350                        self.apply_notify_global_observers_effect(global_type);
1351                    }
1352
1353                    Effect::Defer { callback } => {
1354                        self.apply_defer_effect(callback);
1355                    }
1356                    Effect::EntityCreated {
1357                        entity,
1358                        tid,
1359                        window,
1360                    } => {
1361                        self.apply_entity_created_effect(entity, tid, window);
1362                    }
1363                }
1364            } else {
1365                #[cfg(any(test, feature = "test-support"))]
1366                for window in self
1367                    .windows
1368                    .values()
1369                    .filter_map(|window| {
1370                        let window = window.as_deref()?;
1371                        window.invalidator.is_dirty().then_some(window.handle)
1372                    })
1373                    .collect::<Vec<_>>()
1374                {
1375                    self.update_window(window, |_, window, cx| window.draw(cx).clear())
1376                        .unwrap();
1377                }
1378
1379                if self.pending_effects.is_empty() {
1380                    break;
1381                }
1382            }
1383        }
1384    }
1385
1386    /// Repeatedly called during `flush_effects` to release any entities whose
1387    /// reference count has become zero. We invoke any release observers before dropping
1388    /// each entity.
1389    fn release_dropped_entities(&mut self) {
1390        loop {
1391            let dropped = self.entities.take_dropped();
1392            if dropped.is_empty() {
1393                break;
1394            }
1395
1396            for (entity_id, mut entity) in dropped {
1397                self.observers.remove(&entity_id);
1398                self.event_listeners.remove(&entity_id);
1399                for release_callback in self.release_listeners.remove(&entity_id) {
1400                    release_callback(entity.as_mut(), self);
1401                }
1402            }
1403        }
1404    }
1405
1406    /// Repeatedly called during `flush_effects` to handle a focused handle being dropped.
1407    fn release_dropped_focus_handles(&mut self) {
1408        self.focus_handles
1409            .clone()
1410            .write()
1411            .retain(|handle_id, focus| {
1412                if focus.ref_count.load(SeqCst) == 0 {
1413                    for window_handle in self.windows() {
1414                        window_handle
1415                            .update(self, |_, window, _| {
1416                                if window.focus == Some(handle_id) {
1417                                    window.blur();
1418                                }
1419                            })
1420                            .unwrap();
1421                    }
1422                    false
1423                } else {
1424                    true
1425                }
1426            });
1427    }
1428
1429    fn apply_notify_effect(&mut self, emitter: EntityId) {
1430        self.pending_notifications.remove(&emitter);
1431
1432        self.observers
1433            .clone()
1434            .retain(&emitter, |handler| handler(self));
1435    }
1436
1437    fn apply_emit_effect(&mut self, emitter: EntityId, event_type: TypeId, event: Box<dyn Any>) {
1438        self.event_listeners
1439            .clone()
1440            .retain(&emitter, |(stored_type, handler)| {
1441                if *stored_type == event_type {
1442                    handler(event.as_ref(), self)
1443                } else {
1444                    true
1445                }
1446            });
1447    }
1448
1449    fn apply_refresh_effect(&mut self) {
1450        for window in self.windows.values_mut() {
1451            if let Some(window) = window.as_deref_mut() {
1452                window.refreshing = true;
1453                window.invalidator.set_dirty(true);
1454            }
1455        }
1456    }
1457
1458    fn apply_notify_global_observers_effect(&mut self, type_id: TypeId) {
1459        self.pending_global_notifications.remove(&type_id);
1460        self.global_observers
1461            .clone()
1462            .retain(&type_id, |observer| observer(self));
1463    }
1464
1465    fn apply_defer_effect(&mut self, callback: Box<dyn FnOnce(&mut Self) + 'static>) {
1466        callback(self);
1467    }
1468
1469    fn apply_entity_created_effect(
1470        &mut self,
1471        entity: AnyEntity,
1472        tid: TypeId,
1473        window: Option<WindowId>,
1474    ) {
1475        self.new_entity_observers.clone().retain(&tid, |observer| {
1476            if let Some(id) = window {
1477                self.update_window_id(id, {
1478                    let entity = entity.clone();
1479                    |_, window, cx| (observer)(entity, &mut Some(window), cx)
1480                })
1481                .expect("All windows should be off the stack when flushing effects");
1482            } else {
1483                (observer)(entity.clone(), &mut None, self)
1484            }
1485            true
1486        });
1487    }
1488
1489    fn update_window_id<T, F>(&mut self, id: WindowId, update: F) -> Result<T>
1490    where
1491        F: FnOnce(AnyView, &mut Window, &mut App) -> T,
1492    {
1493        self.update(|cx| {
1494            let mut window = cx.windows.get_mut(id)?.take()?;
1495
1496            let root_view = window.root.clone().unwrap();
1497
1498            cx.window_update_stack.push(window.handle.id);
1499            let result = update(root_view, &mut window, cx);
1500            fn trail(id: WindowId, window: Box<Window>, cx: &mut App) -> Option<()> {
1501                cx.window_update_stack.pop();
1502
1503                if window.removed {
1504                    cx.window_handles.remove(&id);
1505                    cx.windows.remove(id);
1506
1507                    cx.window_closed_observers.clone().retain(&(), |callback| {
1508                        callback(cx);
1509                        true
1510                    });
1511
1512                    let quit_on_empty = match cx.quit_mode {
1513                        QuitMode::Explicit => false,
1514                        QuitMode::LastWindowClosed => true,
1515                        QuitMode::Default => cfg!(not(target_os = "macos")),
1516                    };
1517
1518                    if quit_on_empty && cx.windows.is_empty() {
1519                        cx.quit();
1520                    }
1521                } else {
1522                    cx.windows.get_mut(id)?.replace(window);
1523                }
1524                Some(())
1525            }
1526            trail(id, window, cx)?;
1527
1528            Some(result)
1529        })
1530        .context("window not found")
1531    }
1532
1533    /// Creates an `AsyncApp`, which can be cloned and has a static lifetime
1534    /// so it can be held across `await` points.
1535    pub fn to_async(&self) -> AsyncApp {
1536        AsyncApp {
1537            app: self.this.clone(),
1538            background_executor: self.background_executor.clone(),
1539            foreground_executor: self.foreground_executor.clone(),
1540        }
1541    }
1542
1543    /// Obtains a reference to the executor, which can be used to spawn futures.
1544    pub fn background_executor(&self) -> &BackgroundExecutor {
1545        &self.background_executor
1546    }
1547
1548    /// Obtains a reference to the executor, which can be used to spawn futures.
1549    pub fn foreground_executor(&self) -> &ForegroundExecutor {
1550        if self.quitting {
1551            panic!("Can't spawn on main thread after on_app_quit")
1552        };
1553        &self.foreground_executor
1554    }
1555
1556    /// Spawns the future returned by the given function on the main thread. The closure will be invoked
1557    /// with [AsyncApp], which allows the application state to be accessed across await points.
1558    #[track_caller]
1559    pub fn spawn<AsyncFn, R>(&self, f: AsyncFn) -> Task<R>
1560    where
1561        AsyncFn: AsyncFnOnce(&mut AsyncApp) -> R + 'static,
1562        R: 'static,
1563    {
1564        if self.quitting {
1565            debug_panic!("Can't spawn on main thread after on_app_quit")
1566        };
1567
1568        let mut cx = self.to_async();
1569
1570        self.foreground_executor
1571            .spawn(async move { f(&mut cx).await }.boxed_local())
1572    }
1573
1574    /// Spawns the future returned by the given function on the main thread with
1575    /// the given priority. The closure will be invoked with [AsyncApp], which
1576    /// allows the application state to be accessed across await points.
1577    pub fn spawn_with_priority<AsyncFn, R>(&self, priority: Priority, f: AsyncFn) -> Task<R>
1578    where
1579        AsyncFn: AsyncFnOnce(&mut AsyncApp) -> R + 'static,
1580        R: 'static,
1581    {
1582        if self.quitting {
1583            debug_panic!("Can't spawn on main thread after on_app_quit")
1584        };
1585
1586        let mut cx = self.to_async();
1587
1588        self.foreground_executor
1589            .spawn_with_priority(priority, async move { f(&mut cx).await }.boxed_local())
1590    }
1591
1592    /// Schedules the given function to be run at the end of the current effect cycle, allowing entities
1593    /// that are currently on the stack to be returned to the app.
1594    pub fn defer(&mut self, f: impl FnOnce(&mut App) + 'static) {
1595        self.push_effect(Effect::Defer {
1596            callback: Box::new(f),
1597        });
1598    }
1599
1600    /// Accessor for the application's asset source, which is provided when constructing the `App`.
1601    pub fn asset_source(&self) -> &Arc<dyn AssetSource> {
1602        &self.asset_source
1603    }
1604
1605    /// Accessor for the text system.
1606    pub fn text_system(&self) -> &Arc<TextSystem> {
1607        &self.text_system
1608    }
1609
1610    /// Check whether a global of the given type has been assigned.
1611    pub fn has_global<G: Global>(&self) -> bool {
1612        self.globals_by_type.contains_key(&TypeId::of::<G>())
1613    }
1614
1615    /// Access the global of the given type. Panics if a global for that type has not been assigned.
1616    #[track_caller]
1617    pub fn global<G: Global>(&self) -> &G {
1618        self.globals_by_type
1619            .get(&TypeId::of::<G>())
1620            .map(|any_state| any_state.downcast_ref::<G>().unwrap())
1621            .with_context(|| format!("no state of type {} exists", type_name::<G>()))
1622            .unwrap()
1623    }
1624
1625    /// Access the global of the given type if a value has been assigned.
1626    pub fn try_global<G: Global>(&self) -> Option<&G> {
1627        self.globals_by_type
1628            .get(&TypeId::of::<G>())
1629            .map(|any_state| any_state.downcast_ref::<G>().unwrap())
1630    }
1631
1632    /// Access the global of the given type mutably. Panics if a global for that type has not been assigned.
1633    #[track_caller]
1634    pub fn global_mut<G: Global>(&mut self) -> &mut G {
1635        let global_type = TypeId::of::<G>();
1636        self.push_effect(Effect::NotifyGlobalObservers { global_type });
1637        self.globals_by_type
1638            .get_mut(&global_type)
1639            .and_then(|any_state| any_state.downcast_mut::<G>())
1640            .with_context(|| format!("no state of type {} exists", type_name::<G>()))
1641            .unwrap()
1642    }
1643
1644    /// Access the global of the given type mutably. A default value is assigned if a global of this type has not
1645    /// yet been assigned.
1646    pub fn default_global<G: Global + Default>(&mut self) -> &mut G {
1647        let global_type = TypeId::of::<G>();
1648        self.push_effect(Effect::NotifyGlobalObservers { global_type });
1649        self.globals_by_type
1650            .entry(global_type)
1651            .or_insert_with(|| Box::<G>::default())
1652            .downcast_mut::<G>()
1653            .unwrap()
1654    }
1655
1656    /// Sets the value of the global of the given type.
1657    pub fn set_global<G: Global>(&mut self, global: G) {
1658        let global_type = TypeId::of::<G>();
1659        self.push_effect(Effect::NotifyGlobalObservers { global_type });
1660        self.globals_by_type.insert(global_type, Box::new(global));
1661    }
1662
1663    /// Clear all stored globals. Does not notify global observers.
1664    #[cfg(any(test, feature = "test-support"))]
1665    pub fn clear_globals(&mut self) {
1666        self.globals_by_type.drain();
1667    }
1668
1669    /// Remove the global of the given type from the app context. Does not notify global observers.
1670    pub fn remove_global<G: Global>(&mut self) -> G {
1671        let global_type = TypeId::of::<G>();
1672        self.push_effect(Effect::NotifyGlobalObservers { global_type });
1673        *self
1674            .globals_by_type
1675            .remove(&global_type)
1676            .unwrap_or_else(|| panic!("no global added for {}", std::any::type_name::<G>()))
1677            .downcast()
1678            .unwrap()
1679    }
1680
1681    /// Register a callback to be invoked when a global of the given type is updated.
1682    pub fn observe_global<G: Global>(
1683        &mut self,
1684        mut f: impl FnMut(&mut Self) + 'static,
1685    ) -> Subscription {
1686        let (subscription, activate) = self.global_observers.insert(
1687            TypeId::of::<G>(),
1688            Box::new(move |cx| {
1689                f(cx);
1690                true
1691            }),
1692        );
1693        self.defer(move |_| activate());
1694        subscription
1695    }
1696
1697    /// Move the global of the given type to the stack.
1698    #[track_caller]
1699    pub(crate) fn lease_global<G: Global>(&mut self) -> GlobalLease<G> {
1700        GlobalLease::new(
1701            self.globals_by_type
1702                .remove(&TypeId::of::<G>())
1703                .with_context(|| format!("no global registered of type {}", type_name::<G>()))
1704                .unwrap(),
1705        )
1706    }
1707
1708    /// Restore the global of the given type after it is moved to the stack.
1709    pub(crate) fn end_global_lease<G: Global>(&mut self, lease: GlobalLease<G>) {
1710        let global_type = TypeId::of::<G>();
1711
1712        self.push_effect(Effect::NotifyGlobalObservers { global_type });
1713        self.globals_by_type.insert(global_type, lease.global);
1714    }
1715
1716    pub(crate) fn new_entity_observer(
1717        &self,
1718        key: TypeId,
1719        value: NewEntityListener,
1720    ) -> Subscription {
1721        let (subscription, activate) = self.new_entity_observers.insert(key, value);
1722        activate();
1723        subscription
1724    }
1725
1726    /// Arrange for the given function to be invoked whenever a view of the specified type is created.
1727    /// The function will be passed a mutable reference to the view along with an appropriate context.
1728    pub fn observe_new<T: 'static>(
1729        &self,
1730        on_new: impl 'static + Fn(&mut T, Option<&mut Window>, &mut Context<T>),
1731    ) -> Subscription {
1732        self.new_entity_observer(
1733            TypeId::of::<T>(),
1734            Box::new(
1735                move |any_entity: AnyEntity, window: &mut Option<&mut Window>, cx: &mut App| {
1736                    any_entity
1737                        .downcast::<T>()
1738                        .unwrap()
1739                        .update(cx, |entity_state, cx| {
1740                            on_new(entity_state, window.as_deref_mut(), cx)
1741                        })
1742                },
1743            ),
1744        )
1745    }
1746
1747    /// Observe the release of a entity. The callback is invoked after the entity
1748    /// has no more strong references but before it has been dropped.
1749    pub fn observe_release<T>(
1750        &self,
1751        handle: &Entity<T>,
1752        on_release: impl FnOnce(&mut T, &mut App) + 'static,
1753    ) -> Subscription
1754    where
1755        T: 'static,
1756    {
1757        let (subscription, activate) = self.release_listeners.insert(
1758            handle.entity_id(),
1759            Box::new(move |entity, cx| {
1760                let entity = entity.downcast_mut().expect("invalid entity type");
1761                on_release(entity, cx)
1762            }),
1763        );
1764        activate();
1765        subscription
1766    }
1767
1768    /// Observe the release of a entity. The callback is invoked after the entity
1769    /// has no more strong references but before it has been dropped.
1770    pub fn observe_release_in<T>(
1771        &self,
1772        handle: &Entity<T>,
1773        window: &Window,
1774        on_release: impl FnOnce(&mut T, &mut Window, &mut App) + 'static,
1775    ) -> Subscription
1776    where
1777        T: 'static,
1778    {
1779        let window_handle = window.handle;
1780        self.observe_release(handle, move |entity, cx| {
1781            let _ = window_handle.update(cx, |_, window, cx| on_release(entity, window, cx));
1782        })
1783    }
1784
1785    /// Register a callback to be invoked when a keystroke is received by the application
1786    /// in any window. Note that this fires after all other action and event mechanisms have resolved
1787    /// and that this API will not be invoked if the event's propagation is stopped.
1788    pub fn observe_keystrokes(
1789        &mut self,
1790        mut f: impl FnMut(&KeystrokeEvent, &mut Window, &mut App) + 'static,
1791    ) -> Subscription {
1792        fn inner(
1793            keystroke_observers: &SubscriberSet<(), KeystrokeObserver>,
1794            handler: KeystrokeObserver,
1795        ) -> Subscription {
1796            let (subscription, activate) = keystroke_observers.insert((), handler);
1797            activate();
1798            subscription
1799        }
1800
1801        inner(
1802            &self.keystroke_observers,
1803            Box::new(move |event, window, cx| {
1804                f(event, window, cx);
1805                true
1806            }),
1807        )
1808    }
1809
1810    /// Register a callback to be invoked when a keystroke is received by the application
1811    /// in any window. Note that this fires _before_ all other action and event mechanisms have resolved
1812    /// unlike [`App::observe_keystrokes`] which fires after. This means that `cx.stop_propagation` calls
1813    /// within interceptors will prevent action dispatch
1814    pub fn intercept_keystrokes(
1815        &mut self,
1816        mut f: impl FnMut(&KeystrokeEvent, &mut Window, &mut App) + 'static,
1817    ) -> Subscription {
1818        fn inner(
1819            keystroke_interceptors: &SubscriberSet<(), KeystrokeObserver>,
1820            handler: KeystrokeObserver,
1821        ) -> Subscription {
1822            let (subscription, activate) = keystroke_interceptors.insert((), handler);
1823            activate();
1824            subscription
1825        }
1826
1827        inner(
1828            &self.keystroke_interceptors,
1829            Box::new(move |event, window, cx| {
1830                f(event, window, cx);
1831                true
1832            }),
1833        )
1834    }
1835
1836    /// Register key bindings.
1837    pub fn bind_keys(&mut self, bindings: impl IntoIterator<Item = KeyBinding>) {
1838        self.keymap.borrow_mut().add_bindings(bindings);
1839        self.pending_effects.push_back(Effect::RefreshWindows);
1840    }
1841
1842    /// Clear all key bindings in the app.
1843    pub fn clear_key_bindings(&mut self) {
1844        self.keymap.borrow_mut().clear();
1845        self.pending_effects.push_back(Effect::RefreshWindows);
1846    }
1847
1848    /// Get all key bindings in the app.
1849    pub fn key_bindings(&self) -> Rc<RefCell<Keymap>> {
1850        self.keymap.clone()
1851    }
1852
1853    /// Register a global handler for actions invoked via the keyboard. These handlers are run at
1854    /// the end of the bubble phase for actions, and so will only be invoked if there are no other
1855    /// handlers or if they called `cx.propagate()`.
1856    pub fn on_action<A: Action>(
1857        &mut self,
1858        listener: impl Fn(&A, &mut Self) + 'static,
1859    ) -> &mut Self {
1860        self.global_action_listeners
1861            .entry(TypeId::of::<A>())
1862            .or_default()
1863            .push(Rc::new(move |action, phase, cx| {
1864                if phase == DispatchPhase::Bubble {
1865                    let action = action.downcast_ref().unwrap();
1866                    listener(action, cx)
1867                }
1868            }));
1869        self
1870    }
1871
1872    /// Event handlers propagate events by default. Call this method to stop dispatching to
1873    /// event handlers with a lower z-index (mouse) or higher in the tree (keyboard). This is
1874    /// the opposite of [`Self::propagate`]. It's also possible to cancel a call to [`Self::propagate`] by
1875    /// calling this method before effects are flushed.
1876    pub fn stop_propagation(&mut self) {
1877        self.propagate_event = false;
1878    }
1879
1880    /// Action handlers stop propagation by default during the bubble phase of action dispatch
1881    /// dispatching to action handlers higher in the element tree. This is the opposite of
1882    /// [`Self::stop_propagation`]. It's also possible to cancel a call to [`Self::stop_propagation`] by calling
1883    /// this method before effects are flushed.
1884    pub fn propagate(&mut self) {
1885        self.propagate_event = true;
1886    }
1887
1888    /// Build an action from some arbitrary data, typically a keymap entry.
1889    pub fn build_action(
1890        &self,
1891        name: &str,
1892        data: Option<serde_json::Value>,
1893    ) -> std::result::Result<Box<dyn Action>, ActionBuildError> {
1894        self.actions.build_action(name, data)
1895    }
1896
1897    /// Get all action names that have been registered. Note that registration only allows for
1898    /// actions to be built dynamically, and is unrelated to binding actions in the element tree.
1899    pub fn all_action_names(&self) -> &[&'static str] {
1900        self.actions.all_action_names()
1901    }
1902
1903    /// Returns key bindings that invoke the given action on the currently focused element, without
1904    /// checking context. Bindings are returned in the order they were added. For display, the last
1905    /// binding should take precedence.
1906    pub fn all_bindings_for_input(&self, input: &[Keystroke]) -> Vec<KeyBinding> {
1907        RefCell::borrow(&self.keymap).all_bindings_for_input(input)
1908    }
1909
1910    /// Get all non-internal actions that have been registered, along with their schemas.
1911    pub fn action_schemas(
1912        &self,
1913        generator: &mut schemars::SchemaGenerator,
1914    ) -> Vec<(&'static str, Option<schemars::Schema>)> {
1915        self.actions.action_schemas(generator)
1916    }
1917
1918    /// Get the schema for a specific action by name.
1919    /// Returns `None` if the action is not found.
1920    /// Returns `Some(None)` if the action exists but has no schema.
1921    /// Returns `Some(Some(schema))` if the action exists and has a schema.
1922    pub fn action_schema_by_name(
1923        &self,
1924        name: &str,
1925        generator: &mut schemars::SchemaGenerator,
1926    ) -> Option<Option<schemars::Schema>> {
1927        self.actions.action_schema_by_name(name, generator)
1928    }
1929
1930    /// Get a map from a deprecated action name to the canonical name.
1931    pub fn deprecated_actions_to_preferred_actions(&self) -> &HashMap<&'static str, &'static str> {
1932        self.actions.deprecated_aliases()
1933    }
1934
1935    /// Get a map from an action name to the deprecation messages.
1936    pub fn action_deprecation_messages(&self) -> &HashMap<&'static str, &'static str> {
1937        self.actions.deprecation_messages()
1938    }
1939
1940    /// Get a map from an action name to the documentation.
1941    pub fn action_documentation(&self) -> &HashMap<&'static str, &'static str> {
1942        self.actions.documentation()
1943    }
1944
1945    /// Register a callback to be invoked when the application is about to quit.
1946    /// It is not possible to cancel the quit event at this point.
1947    pub fn on_app_quit<Fut>(
1948        &self,
1949        mut on_quit: impl FnMut(&mut App) -> Fut + 'static,
1950    ) -> Subscription
1951    where
1952        Fut: 'static + Future<Output = ()>,
1953    {
1954        let (subscription, activate) = self.quit_observers.insert(
1955            (),
1956            Box::new(move |cx| {
1957                let future = on_quit(cx);
1958                future.boxed_local()
1959            }),
1960        );
1961        activate();
1962        subscription
1963    }
1964
1965    /// Register a callback to be invoked when the application is about to restart.
1966    ///
1967    /// These callbacks are called before any `on_app_quit` callbacks.
1968    pub fn on_app_restart(&self, mut on_restart: impl 'static + FnMut(&mut App)) -> Subscription {
1969        let (subscription, activate) = self.restart_observers.insert(
1970            (),
1971            Box::new(move |cx| {
1972                on_restart(cx);
1973                true
1974            }),
1975        );
1976        activate();
1977        subscription
1978    }
1979
1980    /// Register a callback to be invoked when a window is closed
1981    /// The window is no longer accessible at the point this callback is invoked.
1982    pub fn on_window_closed(&self, mut on_closed: impl FnMut(&mut App) + 'static) -> Subscription {
1983        let (subscription, activate) = self.window_closed_observers.insert((), Box::new(on_closed));
1984        activate();
1985        subscription
1986    }
1987
1988    pub(crate) fn clear_pending_keystrokes(&mut self) {
1989        for window in self.windows() {
1990            window
1991                .update(self, |_, window, cx| {
1992                    if window.pending_input_keystrokes().is_some() {
1993                        window.clear_pending_keystrokes();
1994                        window.pending_input_changed(cx);
1995                    }
1996                })
1997                .ok();
1998        }
1999    }
2000
2001    /// Checks if the given action is bound in the current context, as defined by the app's current focus,
2002    /// the bindings in the element tree, and any global action listeners.
2003    pub fn is_action_available(&mut self, action: &dyn Action) -> bool {
2004        let mut action_available = false;
2005        if let Some(window) = self.active_window()
2006            && let Ok(window_action_available) =
2007                window.update(self, |_, window, cx| window.is_action_available(action, cx))
2008        {
2009            action_available = window_action_available;
2010        }
2011
2012        action_available
2013            || self
2014                .global_action_listeners
2015                .contains_key(&action.as_any().type_id())
2016    }
2017
2018    /// Sets the menu bar for this application. This will replace any existing menu bar.
2019    pub fn set_menus(&self, menus: Vec<Menu>) {
2020        self.platform.set_menus(menus, &self.keymap.borrow());
2021    }
2022
2023    /// Gets the menu bar for this application.
2024    pub fn get_menus(&self) -> Option<Vec<OwnedMenu>> {
2025        self.platform.get_menus()
2026    }
2027
2028    /// Sets the right click menu for the app icon in the dock
2029    pub fn set_dock_menu(&self, menus: Vec<MenuItem>) {
2030        self.platform.set_dock_menu(menus, &self.keymap.borrow())
2031    }
2032
2033    /// Performs the action associated with the given dock menu item, only used on Windows for now.
2034    pub fn perform_dock_menu_action(&self, action: usize) {
2035        self.platform.perform_dock_menu_action(action);
2036    }
2037
2038    /// Adds given path to the bottom of the list of recent paths for the application.
2039    /// The list is usually shown on the application icon's context menu in the dock,
2040    /// and allows to open the recent files via that context menu.
2041    /// If the path is already in the list, it will be moved to the bottom of the list.
2042    pub fn add_recent_document(&self, path: &Path) {
2043        self.platform.add_recent_document(path);
2044    }
2045
2046    /// Updates the jump list with the updated list of recent paths for the application, only used on Windows for now.
2047    /// Note that this also sets the dock menu on Windows.
2048    pub fn update_jump_list(
2049        &self,
2050        menus: Vec<MenuItem>,
2051        entries: Vec<SmallVec<[PathBuf; 2]>>,
2052    ) -> Task<Vec<SmallVec<[PathBuf; 2]>>> {
2053        self.platform.update_jump_list(menus, entries)
2054    }
2055
2056    /// Dispatch an action to the currently active window or global action handler
2057    /// See [`crate::Action`] for more information on how actions work
2058    pub fn dispatch_action(&mut self, action: &dyn Action) {
2059        if let Some(active_window) = self.active_window() {
2060            active_window
2061                .update(self, |_, window, cx| {
2062                    window.dispatch_action(action.boxed_clone(), cx)
2063                })
2064                .log_err();
2065        } else {
2066            self.dispatch_global_action(action);
2067        }
2068    }
2069
2070    fn dispatch_global_action(&mut self, action: &dyn Action) {
2071        self.propagate_event = true;
2072
2073        if let Some(mut global_listeners) = self
2074            .global_action_listeners
2075            .remove(&action.as_any().type_id())
2076        {
2077            for listener in &global_listeners {
2078                listener(action.as_any(), DispatchPhase::Capture, self);
2079                if !self.propagate_event {
2080                    break;
2081                }
2082            }
2083
2084            global_listeners.extend(
2085                self.global_action_listeners
2086                    .remove(&action.as_any().type_id())
2087                    .unwrap_or_default(),
2088            );
2089
2090            self.global_action_listeners
2091                .insert(action.as_any().type_id(), global_listeners);
2092        }
2093
2094        if self.propagate_event
2095            && let Some(mut global_listeners) = self
2096                .global_action_listeners
2097                .remove(&action.as_any().type_id())
2098        {
2099            for listener in global_listeners.iter().rev() {
2100                listener(action.as_any(), DispatchPhase::Bubble, self);
2101                if !self.propagate_event {
2102                    break;
2103                }
2104            }
2105
2106            global_listeners.extend(
2107                self.global_action_listeners
2108                    .remove(&action.as_any().type_id())
2109                    .unwrap_or_default(),
2110            );
2111
2112            self.global_action_listeners
2113                .insert(action.as_any().type_id(), global_listeners);
2114        }
2115    }
2116
2117    /// Is there currently something being dragged?
2118    pub fn has_active_drag(&self) -> bool {
2119        self.active_drag.is_some()
2120    }
2121
2122    /// Gets the cursor style of the currently active drag operation.
2123    pub fn active_drag_cursor_style(&self) -> Option<CursorStyle> {
2124        self.active_drag.as_ref().and_then(|drag| drag.cursor_style)
2125    }
2126
2127    /// Stops active drag and clears any related effects.
2128    pub fn stop_active_drag(&mut self, window: &mut Window) -> bool {
2129        if self.active_drag.is_some() {
2130            self.active_drag = None;
2131            window.refresh();
2132            true
2133        } else {
2134            false
2135        }
2136    }
2137
2138    /// Sets the cursor style for the currently active drag operation.
2139    pub fn set_active_drag_cursor_style(
2140        &mut self,
2141        cursor_style: CursorStyle,
2142        window: &mut Window,
2143    ) -> bool {
2144        if let Some(ref mut drag) = self.active_drag {
2145            drag.cursor_style = Some(cursor_style);
2146            window.refresh();
2147            true
2148        } else {
2149            false
2150        }
2151    }
2152
2153    /// Set the prompt renderer for GPUI. This will replace the default or platform specific
2154    /// prompts with this custom implementation.
2155    pub fn set_prompt_builder(
2156        &mut self,
2157        renderer: impl Fn(
2158            PromptLevel,
2159            &str,
2160            Option<&str>,
2161            &[PromptButton],
2162            PromptHandle,
2163            &mut Window,
2164            &mut App,
2165        ) -> RenderablePromptHandle
2166        + 'static,
2167    ) {
2168        self.prompt_builder = Some(PromptBuilder::Custom(Box::new(renderer)));
2169    }
2170
2171    /// Reset the prompt builder to the default implementation.
2172    pub fn reset_prompt_builder(&mut self) {
2173        self.prompt_builder = Some(PromptBuilder::Default);
2174    }
2175
2176    /// Remove an asset from GPUI's cache
2177    pub fn remove_asset<A: Asset>(&mut self, source: &A::Source) {
2178        let asset_id = (TypeId::of::<A>(), hash(source));
2179        self.loading_assets.remove(&asset_id);
2180    }
2181
2182    /// Asynchronously load an asset, if the asset hasn't finished loading this will return None.
2183    ///
2184    /// Note that the multiple calls to this method will only result in one `Asset::load` call at a
2185    /// time, and the results of this call will be cached
2186    pub fn fetch_asset<A: Asset>(&mut self, source: &A::Source) -> (Shared<Task<A::Output>>, bool) {
2187        let asset_id = (TypeId::of::<A>(), hash(source));
2188        let mut is_first = false;
2189        let task = self
2190            .loading_assets
2191            .remove(&asset_id)
2192            .map(|boxed_task| *boxed_task.downcast::<Shared<Task<A::Output>>>().unwrap())
2193            .unwrap_or_else(|| {
2194                is_first = true;
2195                let future = A::load(source.clone(), self);
2196
2197                self.background_executor().spawn(future).shared()
2198            });
2199
2200        self.loading_assets.insert(asset_id, Box::new(task.clone()));
2201
2202        (task, is_first)
2203    }
2204
2205    /// Obtain a new [`FocusHandle`], which allows you to track and manipulate the keyboard focus
2206    /// for elements rendered within this window.
2207    #[track_caller]
2208    pub fn focus_handle(&self) -> FocusHandle {
2209        FocusHandle::new(&self.focus_handles)
2210    }
2211
2212    /// Tell GPUI that an entity has changed and observers of it should be notified.
2213    pub fn notify(&mut self, entity_id: EntityId) {
2214        let window_invalidators = mem::take(
2215            self.window_invalidators_by_entity
2216                .entry(entity_id)
2217                .or_default(),
2218        );
2219
2220        if window_invalidators.is_empty() {
2221            if self.pending_notifications.insert(entity_id) {
2222                self.pending_effects
2223                    .push_back(Effect::Notify { emitter: entity_id });
2224            }
2225        } else {
2226            for invalidator in window_invalidators.values() {
2227                invalidator.invalidate_view(entity_id, self);
2228            }
2229        }
2230
2231        self.window_invalidators_by_entity
2232            .insert(entity_id, window_invalidators);
2233    }
2234
2235    /// Returns the name for this [`App`].
2236    #[cfg(any(test, feature = "test-support", debug_assertions))]
2237    pub fn get_name(&self) -> Option<&'static str> {
2238        self.name
2239    }
2240
2241    /// Returns `true` if the platform file picker supports selecting a mix of files and directories.
2242    pub fn can_select_mixed_files_and_dirs(&self) -> bool {
2243        self.platform.can_select_mixed_files_and_dirs()
2244    }
2245
2246    /// Removes an image from the sprite atlas on all windows.
2247    ///
2248    /// If the current window is being updated, it will be removed from `App.windows`, you can use `current_window` to specify the current window.
2249    /// This is a no-op if the image is not in the sprite atlas.
2250    pub fn drop_image(&mut self, image: Arc<RenderImage>, current_window: Option<&mut Window>) {
2251        // remove the texture from all other windows
2252        for window in self.windows.values_mut().flatten() {
2253            _ = window.drop_image(image.clone());
2254        }
2255
2256        // remove the texture from the current window
2257        if let Some(window) = current_window {
2258            _ = window.drop_image(image);
2259        }
2260    }
2261
2262    /// Sets the renderer for the inspector.
2263    #[cfg(any(feature = "inspector", debug_assertions))]
2264    pub fn set_inspector_renderer(&mut self, f: crate::InspectorRenderer) {
2265        self.inspector_renderer = Some(f);
2266    }
2267
2268    /// Registers a renderer specific to an inspector state.
2269    #[cfg(any(feature = "inspector", debug_assertions))]
2270    pub fn register_inspector_element<T: 'static, R: crate::IntoElement>(
2271        &mut self,
2272        f: impl 'static + Fn(crate::InspectorElementId, &T, &mut Window, &mut App) -> R,
2273    ) {
2274        self.inspector_element_registry.register(f);
2275    }
2276
2277    /// Initializes gpui's default colors for the application.
2278    ///
2279    /// These colors can be accessed through `cx.default_colors()`.
2280    pub fn init_colors(&mut self) {
2281        self.set_global(GlobalColors(Arc::new(Colors::default())));
2282    }
2283}
2284
2285impl AppContext for App {
2286    /// Builds an entity that is owned by the application.
2287    ///
2288    /// The given function will be invoked with a [`Context`] and must return an object representing the entity. An
2289    /// [`Entity`] handle will be returned, which can be used to access the entity in a context.
2290    fn new<T: 'static>(&mut self, build_entity: impl FnOnce(&mut Context<T>) -> T) -> Entity<T> {
2291        self.update(|cx| {
2292            let slot = cx.entities.reserve();
2293            let handle = slot.clone();
2294            let entity = build_entity(&mut Context::new_context(cx, slot.downgrade()));
2295
2296            cx.push_effect(Effect::EntityCreated {
2297                entity: handle.clone().into_any(),
2298                tid: TypeId::of::<T>(),
2299                window: cx.window_update_stack.last().cloned(),
2300            });
2301
2302            cx.entities.insert(slot, entity);
2303            handle
2304        })
2305    }
2306
2307    fn reserve_entity<T: 'static>(&mut self) -> Reservation<T> {
2308        Reservation(self.entities.reserve())
2309    }
2310
2311    fn insert_entity<T: 'static>(
2312        &mut self,
2313        reservation: Reservation<T>,
2314        build_entity: impl FnOnce(&mut Context<T>) -> T,
2315    ) -> Entity<T> {
2316        self.update(|cx| {
2317            let slot = reservation.0;
2318            let entity = build_entity(&mut Context::new_context(cx, slot.downgrade()));
2319            cx.entities.insert(slot, entity)
2320        })
2321    }
2322
2323    /// Updates the entity referenced by the given handle. The function is passed a mutable reference to the
2324    /// entity along with a `Context` for the entity.
2325    fn update_entity<T: 'static, R>(
2326        &mut self,
2327        handle: &Entity<T>,
2328        update: impl FnOnce(&mut T, &mut Context<T>) -> R,
2329    ) -> R {
2330        self.update(|cx| {
2331            let mut entity = cx.entities.lease(handle);
2332            let result = update(
2333                &mut entity,
2334                &mut Context::new_context(cx, handle.downgrade()),
2335            );
2336            cx.entities.end_lease(entity);
2337            result
2338        })
2339    }
2340
2341    fn as_mut<'a, T>(&'a mut self, handle: &Entity<T>) -> GpuiBorrow<'a, T>
2342    where
2343        T: 'static,
2344    {
2345        GpuiBorrow::new(handle.clone(), self)
2346    }
2347
2348    fn read_entity<T, R>(&self, handle: &Entity<T>, read: impl FnOnce(&T, &App) -> R) -> R
2349    where
2350        T: 'static,
2351    {
2352        let entity = self.entities.read(handle);
2353        read(entity, self)
2354    }
2355
2356    fn update_window<T, F>(&mut self, handle: AnyWindowHandle, update: F) -> Result<T>
2357    where
2358        F: FnOnce(AnyView, &mut Window, &mut App) -> T,
2359    {
2360        self.update_window_id(handle.id, update)
2361    }
2362
2363    fn read_window<T, R>(
2364        &self,
2365        window: &WindowHandle<T>,
2366        read: impl FnOnce(Entity<T>, &App) -> R,
2367    ) -> Result<R>
2368    where
2369        T: 'static,
2370    {
2371        let window = self
2372            .windows
2373            .get(window.id)
2374            .context("window not found")?
2375            .as_deref()
2376            .expect("attempted to read a window that is already on the stack");
2377
2378        let root_view = window.root.clone().unwrap();
2379        let view = root_view
2380            .downcast::<T>()
2381            .map_err(|_| anyhow!("root view's type has changed"))?;
2382
2383        Ok(read(view, self))
2384    }
2385
2386    fn background_spawn<R>(&self, future: impl Future<Output = R> + Send + 'static) -> Task<R>
2387    where
2388        R: Send + 'static,
2389    {
2390        self.background_executor.spawn(future)
2391    }
2392
2393    fn read_global<G, R>(&self, callback: impl FnOnce(&G, &App) -> R) -> R
2394    where
2395        G: Global,
2396    {
2397        let mut g = self.global::<G>();
2398        callback(g, self)
2399    }
2400}
2401
2402/// These effects are processed at the end of each application update cycle.
2403pub(crate) enum Effect {
2404    Notify {
2405        emitter: EntityId,
2406    },
2407    Emit {
2408        emitter: EntityId,
2409        event_type: TypeId,
2410        event: Box<dyn Any>,
2411    },
2412    RefreshWindows,
2413    NotifyGlobalObservers {
2414        global_type: TypeId,
2415    },
2416    Defer {
2417        callback: Box<dyn FnOnce(&mut App) + 'static>,
2418    },
2419    EntityCreated {
2420        entity: AnyEntity,
2421        tid: TypeId,
2422        window: Option<WindowId>,
2423    },
2424}
2425
2426impl std::fmt::Debug for Effect {
2427    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
2428        match self {
2429            Effect::Notify { emitter } => write!(f, "Notify({})", emitter),
2430            Effect::Emit { emitter, .. } => write!(f, "Emit({:?})", emitter),
2431            Effect::RefreshWindows => write!(f, "RefreshWindows"),
2432            Effect::NotifyGlobalObservers { global_type } => {
2433                write!(f, "NotifyGlobalObservers({:?})", global_type)
2434            }
2435            Effect::Defer { .. } => write!(f, "Defer(..)"),
2436            Effect::EntityCreated { entity, .. } => write!(f, "EntityCreated({:?})", entity),
2437        }
2438    }
2439}
2440
2441/// Wraps a global variable value during `update_global` while the value has been moved to the stack.
2442pub(crate) struct GlobalLease<G: Global> {
2443    global: Box<dyn Any>,
2444    global_type: PhantomData<G>,
2445}
2446
2447impl<G: Global> GlobalLease<G> {
2448    fn new(global: Box<dyn Any>) -> Self {
2449        GlobalLease {
2450            global,
2451            global_type: PhantomData,
2452        }
2453    }
2454}
2455
2456impl<G: Global> Deref for GlobalLease<G> {
2457    type Target = G;
2458
2459    fn deref(&self) -> &Self::Target {
2460        self.global.downcast_ref().unwrap()
2461    }
2462}
2463
2464impl<G: Global> DerefMut for GlobalLease<G> {
2465    fn deref_mut(&mut self) -> &mut Self::Target {
2466        self.global.downcast_mut().unwrap()
2467    }
2468}
2469
2470/// Contains state associated with an active drag operation, started by dragging an element
2471/// within the window or by dragging into the app from the underlying platform.
2472pub struct AnyDrag {
2473    /// The view used to render this drag
2474    pub view: AnyView,
2475
2476    /// The value of the dragged item, to be dropped
2477    pub value: Arc<dyn Any>,
2478
2479    /// This is used to render the dragged item in the same place
2480    /// on the original element that the drag was initiated
2481    pub cursor_offset: Point<Pixels>,
2482
2483    /// The cursor style to use while dragging
2484    pub cursor_style: Option<CursorStyle>,
2485}
2486
2487/// Contains state associated with a tooltip. You'll only need this struct if you're implementing
2488/// tooltip behavior on a custom element. Otherwise, use [Div::tooltip](crate::Interactivity::tooltip).
2489#[derive(Clone)]
2490pub struct AnyTooltip {
2491    /// The view used to display the tooltip
2492    pub view: AnyView,
2493
2494    /// The absolute position of the mouse when the tooltip was deployed.
2495    pub mouse_position: Point<Pixels>,
2496
2497    /// Given the bounds of the tooltip, checks whether the tooltip should still be visible and
2498    /// updates its state accordingly. This is needed atop the hovered element's mouse move handler
2499    /// to handle the case where the element is not painted (e.g. via use of `visible_on_hover`).
2500    pub check_visible_and_update: Rc<dyn Fn(Bounds<Pixels>, &mut Window, &mut App) -> bool>,
2501}
2502
2503/// A keystroke event, and potentially the associated action
2504#[derive(Debug)]
2505pub struct KeystrokeEvent {
2506    /// The keystroke that occurred
2507    pub keystroke: Keystroke,
2508
2509    /// The action that was resolved for the keystroke, if any
2510    pub action: Option<Box<dyn Action>>,
2511
2512    /// The context stack at the time
2513    pub context_stack: Vec<KeyContext>,
2514}
2515
2516struct NullHttpClient;
2517
2518impl HttpClient for NullHttpClient {
2519    fn send(
2520        &self,
2521        _req: http_client::Request<http_client::AsyncBody>,
2522    ) -> futures::future::BoxFuture<
2523        'static,
2524        anyhow::Result<http_client::Response<http_client::AsyncBody>>,
2525    > {
2526        async move {
2527            anyhow::bail!("No HttpClient available");
2528        }
2529        .boxed()
2530    }
2531
2532    fn user_agent(&self) -> Option<&http_client::http::HeaderValue> {
2533        None
2534    }
2535
2536    fn proxy(&self) -> Option<&Url> {
2537        None
2538    }
2539}
2540
2541/// A mutable reference to an entity owned by GPUI
2542pub struct GpuiBorrow<'a, T> {
2543    inner: Option<Lease<T>>,
2544    app: &'a mut App,
2545}
2546
2547impl<'a, T: 'static> GpuiBorrow<'a, T> {
2548    fn new(inner: Entity<T>, app: &'a mut App) -> Self {
2549        app.start_update();
2550        let lease = app.entities.lease(&inner);
2551        Self {
2552            inner: Some(lease),
2553            app,
2554        }
2555    }
2556}
2557
2558impl<'a, T: 'static> std::borrow::Borrow<T> for GpuiBorrow<'a, T> {
2559    fn borrow(&self) -> &T {
2560        self.inner.as_ref().unwrap().borrow()
2561    }
2562}
2563
2564impl<'a, T: 'static> std::borrow::BorrowMut<T> for GpuiBorrow<'a, T> {
2565    fn borrow_mut(&mut self) -> &mut T {
2566        self.inner.as_mut().unwrap().borrow_mut()
2567    }
2568}
2569
2570impl<'a, T: 'static> std::ops::Deref for GpuiBorrow<'a, T> {
2571    type Target = T;
2572
2573    fn deref(&self) -> &Self::Target {
2574        self.inner.as_ref().unwrap()
2575    }
2576}
2577
2578impl<'a, T: 'static> std::ops::DerefMut for GpuiBorrow<'a, T> {
2579    fn deref_mut(&mut self) -> &mut T {
2580        self.inner.as_mut().unwrap()
2581    }
2582}
2583
2584impl<'a, T> Drop for GpuiBorrow<'a, T> {
2585    fn drop(&mut self) {
2586        let lease = self.inner.take().unwrap();
2587        self.app.notify(lease.id);
2588        self.app.entities.end_lease(lease);
2589        self.app.finish_update();
2590    }
2591}
2592
2593impl Drop for App {
2594    fn drop(&mut self) {
2595        self.foreground_executor.close();
2596        self.background_executor.close();
2597    }
2598}
2599
2600#[cfg(test)]
2601mod test {
2602    use std::{cell::RefCell, rc::Rc};
2603
2604    use crate::{AppContext, TestAppContext};
2605
2606    #[test]
2607    fn test_gpui_borrow() {
2608        let cx = TestAppContext::single();
2609        let observation_count = Rc::new(RefCell::new(0));
2610
2611        let state = cx.update(|cx| {
2612            let state = cx.new(|_| false);
2613            cx.observe(&state, {
2614                let observation_count = observation_count.clone();
2615                move |_, _| {
2616                    let mut count = observation_count.borrow_mut();
2617                    *count += 1;
2618                }
2619            })
2620            .detach();
2621
2622            state
2623        });
2624
2625        cx.update(|cx| {
2626            // Calling this like this so that we don't clobber the borrow_mut above
2627            *std::borrow::BorrowMut::borrow_mut(&mut state.as_mut(cx)) = true;
2628        });
2629
2630        cx.update(|cx| {
2631            state.write(cx, false);
2632        });
2633
2634        assert_eq!(*observation_count.borrow(), 2);
2635    }
2636}